linux-kernel - [tip: x86/core] x86/text-patching: Make text_gen_insn() play nice with ANNOTATE

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Date:   Wed, 09 Mar 2022 07:55:11 -0000
From:   "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: x86/core] x86/text-patching: Make text_gen_insn() play nice
 with ANNOTATE_NOENDBR

The following commit has been merged into the x86/core branch of tip:

Commit-ID:     dbf45ea73312b99208809c3b7a4831d6bb4e6ed8
Gitweb:        https://git.kernel.org/tip/dbf45ea73312b99208809c3b7a4831d6bb4e6ed8
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Tue, 08 Mar 2022 16:30:19 +01:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Tue, 08 Mar 2022 23:53:28 +01:00

x86/text-patching: Make text_gen_insn() play nice with ANNOTATE_NOENDBR

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Josh Poimboeuf <jpoimboe@...hat.com>
Link: https://lore.kernel.org/r/20220308154317.638561109@infradead.org
---
 arch/x86/include/asm/text-patching.h | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/text-patching.h b/arch/x86/include/asm/text-patching.h
index b742178..1c4cfb1 100644
--- a/arch/x86/include/asm/text-patching.h
+++ b/arch/x86/include/asm/text-patching.h
@@ -101,13 +101,21 @@ void *text_gen_insn(u8 opcode, const void *addr, const void *dest)
 	static union text_poke_insn insn; /* per instance */
 	int size = text_opcode_size(opcode);
 
+	/*
+	 * Hide the addresses to avoid the compiler folding in constants when
+	 * referencing code, these can mess up annotations like
+	 * ANNOTATE_NOENDBR.
+	 */
+	OPTIMIZER_HIDE_VAR(addr);
+	OPTIMIZER_HIDE_VAR(dest);
+
 	insn.opcode = opcode;
 
 	if (size > 1) {
 		insn.disp = (long)dest - (long)(addr + size);
 		if (size == 2) {
 			/*
-			 * Ensure that for JMP9 the displacement
+			 * Ensure that for JMP8 the displacement
 			 * actually fits the signed byte.
 			 */
 			BUG_ON((insn.disp >> 31) != (insn.disp >> 7));